In many internal combustion engines disposed in a vehicle such as an automobile and the like, a catalyst for purifying exhaust gases is provided in an exhaust path of the engine in order to achieve exhaust gas purification. The catalyst is activated at given temperatures thereof to perform an exhaust-purifying function. To accomplish this, the catalyst preferably maintains preset temperatures so as to exercise a full degree of exhaust-purifying performance.
Also, in some internal combustion engines for use in vehicles, a fuel injection control system is provided for attempting to meet problems with noxious exhaust ingredients, specific fuel consumption, and the like. Variations in an operating state of the internal combustion engine, such as engine loads, an engine speed, cooling water temperatures, and an intake air quantity, are entered into the fuel injection control system as electric signals. The fuel injection control system then actuates fuel injection valves with each period of ignition according to values of the electric signals. A fuel injection quantity is thereby controlled.
Examples of the above are disclosed by Japanese Patent Application Laid-Open No. 61-76741 and Japanese Patent Application Laid-Open No. 2-259279.
According to one example of the above Application No. 61-76741, when steady-state travel of a vehicle is continued, ignition timing is retarded to prevent catalyst temperatures from dropping below predetermined temperatures thereof. At the same time, a power deficiency due to retarded ignition timing is compensated by an idle speed control valve being opened.
According to the other example of above Application No. 2-259279, when a rotational frequency during idling is lower than its target value, reference ignition timing is corrected for an advance angle side so as to produce ignition of the internal combustion engine in a thus corrected setting. Engine power is thereby increased to raise the rotational frequency. When the rotational frequency is higher than its target value, the reference ignition timing is corrected for a delay angle side so as to lower the rotational frequency. This Continual feedback of the rotational frequency converges the engine speed on its target value. When the engine has a lower temperature, the reference ignition timing during idling is set to the delay angle side by a corresponding amount. Stable idling running is thereby provided even at cold temperatures of the engine. This also encourages the catalyst to accelerate engine warm-up, while enhancing both stability of engine idling speed and engine stalling-resistance to external loads at cold temperatures of the engine.
Also, in the internal combustion engine with the fuel injection control system, in order to promote activity of a catalyst by a rise in catalyst temperatures at the time of low temperature-starting of the engine, ignition timing is delayed by a given angle (for example, four degrees) under the control of an electronic-controlled ignition control device for a given length of time or until a predetermined cooling water temperature is reached after the internal combustion engine is started. The combustion state is thereby changed.
In previous fuel injection control systems for use in an internal combustion engine, ignition timing is delayed by a fixed value (four degrees) at the time of low temperature-starting of the internal combustion engine, to change the combustion state so as to raise catalyst temperatures. However, the rate of rise in catalyst temperatures is too low to sufficiently curtail noxious exhaust ingredients such as high carbon and the like. Thus, there is an inconvenience in that retarded ignition timing alone fails to sufficiently activate the catalyst. In addition, in view of noxious exhaust ingredient-related regulations, which have recently been even more tightened, simply retarded ignition timing has a disadvantage in its inability to meet these regulations. Furthermore, there is another inconvenience in that such retarded ignition timing detracts from operability at a light-loaded operation phase of the internal combustion engine.
In order to eliminate the above-mentioned inconveniences, the present invention provides a fuel injection control system for use in an internal combustion engine having a catalyst at its exhaust path, characterized in that: each cylinder is provided with a fuel injection valve for injecting fuel thereinto amounting to a reference injection quantity which is set according to a loaded state of the internal combustion engine; each cylinder is provided with a spark plug for producing spark ignition therein at each period of reference ignition timing which is established according to the loaded state of the internal combustion engine; and, the fuel injection control system is provided with a controlling means, which controls the fuel injection valve such as to increase and decrease the reference fuel injection quantity by a different amount per cylinder without a change in a total of the reference fuel injection quantity, and in addition varies this fuel increase and decrease according to the loaded state of the internal combustion engine; the controlling means further controls the spark plug such as to retard the reference ignition timing by an amount different from one cylinder to another, and in addition varies this retardation according to the loaded state of the internal combustion engine, such control being effected when the internal combustion engine is in an operating state which conforms to predetermined conditions.
According to the above structure of the present invention, when an internal combustion engine is operated in a state which complies with predetermined conditions, a reference fuel injection quantity is regulated by a controlling means so as to increase or decrease by an amount varying with cylinders without a change in a total of the reference fuel injection quantity. At the same time, such a fuel increase or decrease is regulated by the controlling means so as to vary according to a loaded state of the internal combustion engine. Furthermore, reference ignition timing is controlled by the controlling means so as to retard by an amount different from one cylinder to another. At the same time, such a retardation is controlled by the controlling means so as to vary according to the loaded state of the internal combustion engine. As a consequence, ignition timing is, of course, retarded; what's more, a fuel injection quantity varies with the cylinders according to the loaded state of the engine, while a total of the fuel injection quantity remains unchanged, thereby feeding fuel thereinto. Moreover, the ignition timing varies with the cylinders in dependence upon the loaded state of the engine, thereby producing spark ignition therein.
The present invention also provides a fuel injection control system for use in an internal combustion engine having multi-cylinders to control injection of fuel into the internal combustion engine by means of fuel injection valves in response to an ignition signal, the fuel injection control system comprising: a controlling means which alters a proportion of a fuel injection quantity between the cylinders while maintaining constant the total amount of fuel injected into the internal combustion engine with each period of ignition when the internal combustion engine is started at low temperatures, the controlling means changing each delay angle of ignition timing per cylinder.
According to the above structure of the present invention, a fuel injection quantity and ignition timing per cylinder are varied with each period of ignition at the time of low temperature-starting of an internal combustion engine, i.e., when a cold engine is started. As a result, catalyst temperatures rise faster than in previous cases, which further accelerates activity of a catalyst. The occurrence of noxious exhaust ingredients can thereby be reduced successfully.